1. Field of the Invention
The present invention relates generally to a structure for supporting a swash plate at the maximum tilt angle in a swash plate type compressor, and more particularly to a structure for supporting a swash plate at the maximum tilt angle in a swash plate type compressor, which is capable of preventing the swash plate from being damaged by eliminating eccentric load caused by differences in the strokes of the pistons.
2. Description of the Prior Art
A compressor constituting one of the principal elements of an air-conditioning apparatus for automobiles is a machine, which selectively receives power from an engine by the intermittence action of a clutch, compresses gaseous refrigerant sucked from an evaporator into its cylinder by the rectilinear reciprocating movement of its piston, and, finally, discharges the refrigerant to a condenser.
Hereinafter, a conventional variable displacement swash plate type compressor is described.
As illustrated in FIGS. 5 to 7, the variable replacement swash plate type compressor comprises a cylinder block 1, in which a plurality of bores 11 are circumferentially arranged and each extended longitudinally. A front housing 3 is positioned in front of the cylinder block 1, and defines a crank chamber 31. A rear housing 4 is positioned behind the cylinder block 1, and defines a suction chamber 41 and a discharge chamber 42. A plurality of pistons 2 are each inserted into a bore 11 of the cylinder block 1 to be moved forward and rearward, and each provided at its rear end with a bridge 21. A drive shaft 6 rotatably passes through the front housing 3, and is rotatably inserted at its rear end into and supported by the center portion of the cylinder 1. A rotor 61 is situated in the interior of the crank chamber 31, and fixedly fitted around and rotates together with the drive shaft 6. A swash plate 7 is fitted around the drive shaft 6 and in the crank chamber 31 to be swung and rotated by support means, such as a bearing or support pin. The swash plate 7 is rotatably supported with its peripheral edge inserted into the bridges 21 of the pistons 2, and hingedly attached at the center portion of the upper portion of its front surface to the rotor 61 to be rotated together with the rotor 61 and to allow its tilt angle to be adjusted with regard to the drive shaft 6. A valve unit 5 is disposed between the cylinder block 1 and the rear housing 4, and functions to suck refrigerant from the suction chamber 41 and to the bores 11 and to discharge compressed refrigerant from the bore 11 to the discharge chamber 42.
A support projection 71, which is brought into contact with the rear surface of the rotor 61 and defines the maximum tilt angle limit of the swash plate 7, is formed on a position of the front surface of the swash plate 7. The tilt angle of the swash plate 7 with regard to the drive shaft 6 is adjusted according to the pressure changes of suction pressure in the rear housing 4 caused by the operation of a control valve 8.
The operation of the swash plate type compressor is described, hereinafter. The pistons 2 arranged in a circle in the cylinder block 1 are sequentially reciprocated by the rotation of the swash plate 7. When a piston 2 moves forward in a bore 11 (that is, during a suction stroke), the suction lead valve of the valve unit 5 is opened by a pressure drop in the bore 11 and the bore 11 communicates with the suction chamber 41, thereby allowing refrigerant to flow from the suction chamber 41 to the bore 11. When a piston 2 moves rearward in a bore 11 (that is, during a compression stroke), the discharge lead valve of the valve unit 5 is opened by a pressure increase in the bore 11 and the bore 11 communicates with the discharge chamber 42, thereby allowing refrigerant to be discharged from the bore 11 to the discharge chamber 42.
In the process of the suction and compression of refrigerant, the swash plate 7 is rotated and the positions of the pistons 2 in their strokes are different, so forces exerted on the swash plate 7 by the pistons 2 are different according to the positions of the swash plate 7 where the pistons 2 are engaged with the swash plate 7. Additionally, as shown in FIG. 9, the support projection 71 defining the maximum tilt angle limit of the swash plate 7 is situated on a connecting line LC passing through the center P1 of the piston 2 in the maximum compression stroke state (that is, the center P1 of the piston 2 at the central position of the upper portion of the swash plate 7, or the center of the bore 11 to which this piston 2 is inserted) and the center P2 of the drive shaft 6 on the front surface of the swash plate 7. However, an acting point P4 of the maximum compression reactive force exerted on the swash plate 7 by the pistons 2 is situated at no a position corresponding to the first point P1 but a position that is spaced apart from the first point P1 by a certain distance L in the rotational direction of the swash plate 7 (see FIG. 8). Accordingly, eccentric load is exerted on the swash plate 7, thereby damaging the swash plate 7 to be bent, deformed or the like. Additionally, when the swash plate 7 is further rotated while being deformed, eccentric wear occurs, thereby creating a loud noise. Additionally, there occurs a problem that the concentration of stress is produced on the hinge unit 64 of the swash plate 7 and the rotor 61.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a structure for supporting a swash plate at the maximum tilt angle in a swash plate type compressor, which is capable of effectively preventing the swash plate from being damaged by preventing eccentric load from acting on the swash plate.
In order to accomplish the above object, the present invention provides a structure for supporting a swash plate at the maximum tilt angle in a swash plate type compressor, in which the swash plate is fitted around a drive shaft by support means to be swung, the peripheral edge of the swash plate is rotatably inserted into the bridges of pistons movably inserted into a plurality of bores formed in a cylinder, the central portion of the upper portion of the front surface of the swash plate is attached by a hinge unit to a rotor fixedly attached around the drive shaft, the center of the hinge unit coincides with the center of the a bore into which a piston at its maximum compression stroke state is inserted, and a support projection is formed at a predetermined position of the front surface of the swash plate to define the maximum tilt angle limit by coming into contact with the rotor, characterized in that: when a connecting line passing through the center of the bore, into which the piston in the maximum compression stroke state is inserted, designated by LC, the support projection is situated on an acting line LP, which is spaced apart from the connecting line LC by a predetermined horizontal distance LF in the rotational direction of the swash plate, so as to define the maximum tilt angle limit of the swash plate.
A diameter of a circle passing through centers of the bores is designated by R, the horizontal distance LF may be in a range of 0.35R to 0.43R.